New, Faster Graphene Transistors

11 January 2009


Simulation of graphene


Scientists at IBM have successfully built the world's fastest graphene transistor.

Transistors are little electronic switches which make use of a small current to switch a large one on and off.  They form the basis of the whole of electronics and computing, so making them work faster is very important in all sorts of areas.

GrapheneToday the limiting factors on how fast they will switch on and off are basically to do with how fast a signal can get from one side of the switch to the other.  You can improve this time by reducing the size of the transistor or making the electrons move more quickly.

For the last 40 years transistors have always been made from silicon so the speed of the electrons, which depends on the material through which they are passing, has been pretty much fixed.  The size of the transistors, however, has reduced hugely, allowing computer speeds to increase from being measured in kilohertz -  thousands of switches per second, to gigahertz - millions of switches per second.  Unfortunately making silicon transistors smaller than 40nm suddenly gets very, very difficult, so we can't rely on this in the future.

Another solution is to use different materials, and one of the most promising is called graphene.  Graphene is a sheet of graphite - the stuff in pencil leads - but only 1-2 atoms thick.  This can behave as a semiconductor, like silicon, so you can make transistors from it, but crucially the speed of the electrons can be up to 100 times that of electrons in silicon so it is very promising for use in transistors.

Graphene was only discovered in 2004 but researchers at IBM have already developed a transistor which will work at up to 26GHz.  This was done with a relatively large, at 150nm, and unoptimised design so whilst it is significantly slower than the fastest silicon transistors, it is still an immense rate of progress.  The researchers are predicting that within a few years they should be able to make transistors that work at terrahertz rates - that's 10,000,000,000,000 switches per second.


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